BUDS AND BRANCHES 101 



94. Structure of winter buds. The scaly buds of our com- 

 mon trees and shrubs are readily picked to pieces as soon 

 as they begin to swell in early spring, but it is easier to dis- 

 tinguish the parts of which they are composed by watching 

 the opening process from the very beginning. Sections of 

 buds, if carefully made, show very clearly the relations of the 

 parts (fig. 85). In a leaf bud there are, on the outside, the 

 leathery bud scales ; inside of these are rudimentary leaves ; 



FIG. 87. Cottonwood twigs, April 15 



The flower buds on the lower twig (developing into catkins) are fully open, but 

 the leaf buds are still closed. Reduced 



and within and below the leaves is a central axis tipped with 

 a growing point composed of rudimentary cells capable of rapid 

 division and growth. 



The scales which cover buds are often the dwarfed and 

 otherwise modified leaves or leafstalks, as is well shown in 

 some buckeyes and in roses in which the opening buds present 

 a series of gradations between mere scales and foliage leaves 

 (fig. 76). In other cases, as in oaks, beeches, lindens, and 

 magnolias, the scales represent the appendages (stipules) found 

 at the bases of many leaves. Frequently bud scales are cov- 

 ered with a den.se layer of hairs or down, and sometimes, as in 



